This invention lies in the field of exhaust gas purifiers, in general, and to a purifier for the effluent from a blister copper furnace, in particular.
Such effluent gases contain large quantities of oxidizable material, and large quantities of particulate matter, in the range in size of from a few microns up to 600 microns or more, and they are at high temperature, in the range of 2100.degree. to 2400.degree..
Copper scrap including attendant foreign materials, such as plastic insulation, fibers and other metallic elements, is melted in a blister furnace. In the first cycle which is called the "charge and melt cycle," the furnace is charged with the copper scrap which forms a slag of debris, which is called scoria. This slag is removed by tilting the furnace and removing the floating scoria from the surface of the liquid copper. However, much of the scoria remains in particulate form in the effluent.
In the charge and melt cycle, oxidizing gases are passed through the molten copper in order to oxidize foreign metallic material, and cause them to form solid oxides in the scoria, or to be blown off as metallic vapors, etc. The oxidation is for the purpose of purifying the copper by removing foreign materials. However, there may be an excess of air, and consequently some oxidization of the copper to cupric oxide.
The next step of the operation is what is called the "poling cycle." This is the step of reducing the copper by injecting into the molten copper a reducing gas, such as hydrogen or carbon monoxide or ammonia or combinations of reduction gases. The amount and kind of gas is carefully controlled so as not to reduce the copper too far.
The volume of effluent during the charge and melt cycle is considerably greater than that during the poling cycle, and may be as much as five times more. This makes it difficult to control the throughput of the effluent in the treating apparatus, because of the different flow rates of effluent.